Valve closure system and valve closure assembly

ABSTRACT

A valve closure assembly ( 50 ) for remotely and automatically closing a railway tank car valve (V 1,  V 2,  V 3,  V 4 ), characterized by improved convenience in mounting on a tank car dome ( 160 ) and adaptability to various dome geometries, valve configurations, and car-to-car dimensional variations. A clamp assembly ( 52 ) mounts assembly ( 50 ) on dome ( 160 ). An adapter ( 180 ) operated by a motor ( 58 ) turns a valve handle (A 1,  A 2,  A 3,  A 4 ) when motor ( 58 ) runs. A positioning mechanism ( 54 ) selectively positions adapter ( 180 ) relative to clamp assembly ( 52 ) to establish a spatial relationship between them for enabling clamp assembly ( 52 ) to be placed at a desired location on the dome wall ( 162 ) and adapter ( 180 ) to engage a valve handle. Positioning mechanism ( 54 ) comprises three degrees of freedom of motion for establishing the spatial relationship of adapter ( 180 ) to clamp assembly ( 52 ), two of which are in the horizontal plane.

REFERENCE TO RELATED APPLICATION AND PRIORITY CLAIM

[0001] This application derives from the following commonly ownedco-pending patent application, the priority of which is expresslyclaimed: Provisional Application No. 60/374,652, filed on Apr. 22, 2002in the names of Richard Fortino and David N. Maniez Jr.

FIELD OF THE INVENTION

[0002] This invention relates to a valve closure system and valveclosure assembly for promptly and automatically closing tank valves,especially tank valves of railway tank cars. The invention also relatesto methods of making and using the valve closure assembly.

BACKGROUND OF THE INVENTION

[0003] Various fluids are transported by railway tank cars. Such tankcars have domes where various valves are located. The portions of thevalves that are external to the tank, including the valve handles arehoused within a protective housing that has a hinged lid or cover thatis opened to expose the handles. One or more of the valves is openedduring certain procedures involving loading and/or unloading fluid intoand/or from the tank. During such procedures, a valve closure assemblyhaving a power actuator is hoisted onto the dome and mounted there. Thepower actuator is fitted to the handle of the open valve and can beremotely and automatically operated to close the open valve whenconditions call for valve closing.

SUMMARY OF THE INVENTION

[0004] The present invention relates to improvements in valve closureassemblies for remotely and automatically closing an open tank car valvewhen conditions call for valve closing. The inventive valve closureassembly is characterized by improved convenience in mounting and use ona railway tank car and by better adaptability to various types ofprotective housings and various tank car valve configurations within thehousings. It is tolerant of car-to-car variations in standard dimensionsthat are promulgated by industry for various valve configurations. Theinventive principles include methods of making and using the valveclosure assembly, and certain aspects of the invention may be useful inother than the context of a railway tank car.

[0005] One generic aspect of the invention relates to an assembly forturning an external handle of a tank dome valve about a vertical axis.The assembly comprises a mounting for removably mounting the assembly ona tank dome and an adapter operated by a motor for engaging the valvehandle and turning the handle when the motor operates. The assemblyfurther comprises a positioning mechanism for selectively positioningthe adapter relative to the mounting to establish a spatial relationshipof each to the other for enabling the mounting to be placed at a desiredlocation on the dome and the adapter to engage the valve handle. Thepositioning mechanism comprises two degrees of freedom of motion in ahorizontal plane for establishing the spatial relationship of theadapter to the mounting in the horizontal plane.

[0006] Another generic aspect of the invention relates to an assemblyfor turning an external handle of a tank dome valve about a verticalaxis where the assembly comprises a mounting for removably mounting theassembly on a tank dome, an adapter operated by a motor for engaging thevalve handle and turning the handle when the motor operates, and apositioning mechanism for selectively positioning the adapter relativeto the mounting to establish a spatial relationship of each to the otherfor enabling the mounting to be placed at a desired location on the domeand the adapter to engage the valve handle. The positioning mechanismcomprises three degrees of freedom of motion for establishing thespatial relationship of the adapter to the mounting.

[0007] Another generic aspect of the invention relates to a method ofassociating a valve operating assembly with a fluid-containing tank forenabling an adapter that is operated by a motor of the valve operatingassembly to turn an external handle of a valve on the tank about an axisof turning while a mounting of the assembly is supporting the assemblyon the tank. The method comprises relatively positioning the mountingand the adapter via a positioning mechanism of the valve operatingassembly that has two degrees of freedom of motion in a plane ofreference that is perpendicular to the axis of turning to establish aspatial relationship of the mounting and motor to each other in theplane of reference for placing the adapter in engagement with the valvehandle and placing the mounting at a desired location on the tank.

[0008] Another generic aspect of the invention relates to a method ofassociating a valve operating assembly with a fluid-containing tank forenabling an adapter operated by a motor of the valve operating assemblyto turn a valve on the tank about an axis of turning while a mounting ofthe assembly is supporting the assembly on the tank wherein the methodcomprises relatively positioning the mounting and the adapter via apositioning mechanism of the valve operating assembly that has threedegrees of freedom of motion to establish a spatial relationship of themounting and motor to each other for placing the adapter in engagementwith the valve handle and placing the mounting at a desired location onthe tank.

[0009] Still another generic aspect of the invention relates to a methodof associating a valve operating assembly comprising a mounting, apositioning mechanism, and an adapter operated by a motor with a dome ofa fluid-containing tank comprising a valve having a handle that isexternal to the tank and an upright wall spaced horizontally from thevalve handle for enabling the adapter to engage the valve handle andturn the handle about an axis of turning while the mounting issupporting the assembly at a desired location on the dome inhorizontally spaced relation to the valve handle. The method comprisesdisposing the valve operating assembly vertically over the dome,lowering the assembly onto the dome, and causing the positioningmechanism to relatively position the mounting and the adapter to placethe adapter in engagement with the valve handle and to place themounting at a desired location on the upright wall.

[0010] The foregoing features, advantages, and aspects of the invention,along with additional ones, will be seen in the ensuing description andclaims, which are accompanied by drawings. The drawings disclose apresently preferred embodiment of the invention according to the bestmode contemplated at this time for carrying out the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011]FIG. 1 is a perspective view showing a presently preferredembodiment of valve closure system comprising a valve closure assemblyaccording to the present invention.

[0012]FIG. 2 is an exploded perspective view of FIG. 1.

[0013]FIG. 3 is a top of plan view of FIG. 1.

[0014]FIG. 4 is a vertical cross section view in the direction of arrows4-4 in FIG. 3.

[0015]FIG. 5 is a vertical cross section view in the direction of arrows5-5 in FIG. 3.

[0016]FIG. 6 is a vertical cross section view in the direction of arrows6-6 in FIG. 3.

[0017]FIG. 7 is a perspective view of a clamp assembly of the valveclosure assembly.

[0018]FIG. 8 is an elevation view in the direction of arrow 8 in FIG. 7.

[0019]FIG. 9 is a right side elevation view of FIG. 8.

[0020]FIG. 10 is a top view of FIG. 9.

[0021]FIG. 11 is a perspective view of one element of the clamp assemblyby itself.

[0022]FIG. 12 is an elevation view in the direction of arrow 12 in FIG.11.

[0023]FIG. 13 is a right side elevation view of FIG. 12.

[0024]FIG. 14 is a top view of FIG. 12.

[0025]FIG. 15 is a perspective view of another element of the clampassembly by itself.

[0026]FIG. 16 is an elevation view in the direction of arrow 16 in FIG.15.

[0027]FIG. 17 is a right side elevation view of FIG. 16.

[0028]FIG. 18 is a top view of FIG. 16.

[0029]FIG. 19 is a perspective view of still another element of theclamp assembly by itself.

[0030]FIG. 20 is an elevation view in the direction of arrow 20 in FIG.19.

[0031]FIG. 21 is a right side elevation view of FIG. 20.

[0032]FIG. 22 is a top view of FIG. 20.

[0033]FIG. 23 is a perspective view of an element of a motor head of thevalve closure assembly by itself.

[0034]FIG. 24 is an elevation view in the direction of arrow 24 in FIG.23.

[0035]FIG. 25 is a left side elevation view of FIG. 24.

[0036]FIG. 26 is a perspective view of another element of the motor headby itself.

[0037]FIG. 27 is an elevation view in the direction of arrow 27 in FIG.26.

[0038]FIG. 28 is a top view of FIG. 27.

[0039]FIG. 29 is a right side view of FIG. 28.

[0040]FIG. 30 is a perspective view of an element of a head positioningmechanism of the valve closure assembly by itself.

[0041]FIG. 31 is a view in the direction of arrow 31 in FIG. 30.

[0042]FIG. 32 is a bottom view of FIG. 31.

[0043]FIG. 33 is a right side view of FIG. 32.

[0044]FIG. 34 is a top plan view of the valve closure assembly mountedon a railway tank car.

[0045]FIG. 35 is a front elevation view of FIG. 34.

[0046]FIG. 36 is a perspective view of a direct drive adapter by itself.

[0047]FIG. 37 is a top plan view of FIG. 36.

[0048]FIG. 38 is a vertical cross section view in the direction ofarrows 38-38 in FIG. 37.

[0049]FIG. 39 is a cross section view in the direction of arrows 39-39in FIG. 36.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0050]FIGS. 1 through 6 illustrate a presently preferred embodiment ofvalve closure assembly 50 of a valve closure system in accordance withprinciples of the invention. The valve closure assembly is adapted formounting on the dome of a railroad tank car and operative coupling witha handle of a valve on the tank car for enabling the valve to beautomatically closed in a situation where immediate valve closure iscalled for.

[0051] The dome of a representative of railroad tank car comprises aprotective housing. The protective housing comprises a circular uprightwall that is supported on a manway cover. The manway cover is supportedon a flange of a circular manway opening in the tank dome. That assemblycarries various valves whose handles are disposed external to the tankinterior, but within the interior of the protective housing. Piping forthe valves extends through the manway cover into the tank interior. Theopen top of the circular upright wall of the protective housing isclosed by a circular cover that can be opened to provide access to theinterior of the protective housing, and hence to the valve handles. Withthe cover open, the rim of the circular wall is exposed.

[0052] The present invention utilizes the exposed rim of the circularwall of the protective housing for securely mounting valve closureassembly 50 on a tank car dome. Valve closure assembly 50 comprises aclamp assembly 52 for clamping on the rim of the circular wall of theprotective housing, a positioning mechanism 54 that is supported on theclamp assembly, and a motor head 56 that is positioned by thepositioning mechanism for operative association with a valve handle thatwill enable system 50 to promptly close the associated valve by turningthe valve handle when called upon to do so.

[0053] Motor head 56 comprises a motor 58, preferably an air motor, thatis mounted upright on a motor mounting 60. Mounting 60 comprises a baseplate 62 that is shown by itself in detail in FIGS. 26 through 29.Mounting 60 is securely fastened to positioning mechanism 54 through arectangular tie bar 64 using screws 66. A bracket 68 is fastened byfastening elements 70, 72 to base plate 62. A handle 74 is in turnfastened to bracket 68 by fasteners 76. Handle 74 comprises a handlebar78 and a grip 80.

[0054] From this description it can be appreciated that mounting 60comprises a horizontal platform on which motor 58 is securely mountedand a vertical wall that extends upward from that platform along sidethe motor. The horizontal portion of base plate 62 forms the horizontalplatform of mounting 60, and the vertical portion of base plate 62 andbracket 68 together form the vertical wall of the mounting. Handle 74extends horizontally away from the side of that vertical wall oppositemotor 58 near the upper end of the motor.

[0055] The shank of a respective headed screw 81 passes through each ofsix holes 83 in base plate 62 to thread into a respective threaded holein an end of the air motor body. Tightening of the screws secures motor58 on motor mounting 60. It is considered desirable to protectivelyenclose motor 58 by a circular cylindrical shield 82. A circular ring 84is disposed around the air motor body at one end and clamped to the airmotor body using three set screws 85 that are threaded into tappedthrough-holes in ring 84. One end of shield 82 fits over ring 84 toestablish concentricity of the shield to the motor body and containsseveral clearance holes that allow the shanks of headed screws 87 topass through and thread into tapped holes in ring 84. These screws aretightened to secure the shield to the ring. An annular ring seal 86closes the annular space between the shield and the motor body at theopposite end. The horizontal platform that base plate 62 provides tosupport motor 58 comprises a central through-hole 89 surrounded by thesix holes 83. Through-hole 89 allows the motor shaft 91 to pass downwardthrough the horizontal platform where a direct drive adapter 180 iscoupled to the shaft using a hitch pin 93. The upper end of motor 58remains exposed to provide for connection of an air line (not shown) tothe motor.

[0056] Positioning mechanism 54 comprises circular cylindrical rods 92,94, linear bearings 96, 98, and a pillow block 100. Rods 92, 94 aredisposed horizontally spaced apart in mutually parallel relationship.Tie bar 64 at one end of rods 92, 94 and a second tie bar 102 at theopposite ends of the rods have counterbored through-holes that allow therod ends to fit with precision to the counterbores of the tie bars.Screws 66 pass through the clearance holes 103 of one of four pairs ofsuch clearance holes in base plate 62 to enter the through-holes in tiebar 64 and thread into tapped holes in the rods. The uppermost pair ofholes 103 are used for fastening bracket 68 to base plate 62, while theother three pairs provides for motor head 56 to be fastened topositioning mechanism 54 at any of three different elevations. Rods 92,94 have tapped holes at their opposite ends, which seat with precisionin the counterbores in the through-holes in tie bar 102. Screws 104fasten tie bar 102 and the rods together at that end in the same way sothat the assembly of the two tie bars and the two rods forms a part ofthe positioning mechanism that can translate horizontally relative topillow block 100.

[0057] Detail of pillow block 100 is shown in FIGS. 30-33. Linearbearings 96, 98 are fit to respective through-holes 106, 108 in pillowblock 100. Rods 92, 94 pass through these linear bearings. Midwaybetween and at a right angle to through-holes 106,108, pillow block 100comprises a vertical through-hole 110. A linear bearing 112 is fit tothrough-hole 110. A circular rod 114 that has tapped holes at oppositeends passes through linear bearing 112. A stop disk 116 is fastened tothe upper end of rod 114 using a screw 118. A screw 120 fastens clampassembly 52 to the lower end of rod 114.

[0058] During the process of assembling positioning mechanism, tubularbumpers 121 are fit onto ends of rods 92, 94 proximate each tie bar 64,102. Bumpers 121 limit the travel of pillow block 100 on rods 92, 94 sothat the pillow block cannot strike either tie bar. The lengths of thebumpers are chosen to also provide sufficient clearance between thepillow block and the tie bars at the limits of pillow block travel sothat pinch points are not present between the pillow block and the tierods at the limits of pillow block travel.

[0059] FIGS. 7-22 show that clamp assembly 52 comprises a bracketassembly 122 fabricated from two base clamp parts 124, 126 and astrengthener plate 128. In addition to bracket assembly 122, clampassembly 52 comprises a hand screw 130 that can be manually turned by aturning knob 159 shown in FIGS. 1-4 and 6.

[0060] Part 126 is shaped to fit onto the rim of the protective housingof a railway tank car and comprises spaced apart vertical side walls132, 134 that are joined by a horizontal top wall 136, endowing the partwith an inverted U-shape as shown by FIG. 17. When the part is fit ontothe protective housing rim, wall 132 is disposed inside the rim, wall134 is disposed outside the rim, and top wall 136 rests on the top edgesurface of the rim. Hence walls 132, 134 are spaced apart a distancethat is greater than the thickness of the protective housing rim.

[0061] Part 124 is shaped to nest on part 126 and comprises a horizontalrectangular top wall 138 and legs 140, 142, 144, 146 depending from thefour corners of top wall 138. In the direction of the thickness of theprotective housing rim, part 124 is longer than part 126, but part 124is shorter than part 126 in a direction at 90° to the thickness of theprotective housing rim. Between leg 140 and leg 142, part 124 has adownwardly open rectangular throat. A like throat exists between leg 144and leg 146. The two throats are dimensioned so that part 124 fitssnuggly onto part 126, as shown in FIGS. 7 and 9.

[0062] Strengthener plate 128 is rectangular in shape and is disposedagainst the outer surface of side wall 134 and between the lower ends oflegs 142, 146. The three parts 124, 126, 128 are aluminum alloy and arejoined together by any suitable metallurgical joining technique to formbracket assembly 122.

[0063] Top wall 138 has a circular hole 150 at its center that allowsthe lower end of rod 114 to pass through and abut top wall 136. Thelatter wall has a countersunk hole 152 for allowing the flat head ofscrew 120 to seat flush in the countersink. Because the two walls 136,138 are spaced vertically apart and rod 114 has a close fit to hole 150,rod 114 is rigidly supported on clamp assembly 52. Rigidity may beenhanced by joining rod 114 to wall 138.

[0064] Strengthener plate 128 comprises a tapped hole 154 into which thethreaded shank 156 of hand screw 130 is threaded. Side wall 134 may havea clearance hole 157 for shank 156, or it may provide an extension ofthe tapped hole in plate 128. Although the thickness of wall 134 may besufficient for the forces that it will experience during use of thevalve closure system, that thickness may be insufficient to provide thedesired length for the tapped hole needed for hand screw 130.Strengthener plate 128 is therefore included to provide the desiredtapped hole length into which shank 156 is threaded.

[0065] FIGS. 34-35 illustrate an example of how valve closure assembly50 is used on a railway tank car. The tank car has a centrally locateddome that has a protective housing 160. The protective housing comprisesa circular upright side wall 162 on which a top cover (not shown) ishinged for opening and closing the housing. Side wall 162 is supportedon a manway cover 164 that is part of an assembly that carries fourvalves V1, V2, V3, V4 in this example. The valves comprise respectivehandles A1, A2, A3, A4 that are disposed external to the tank interior,but within the interior of housing 160. With the top cover swung open,the rim of side wall 162 is exposed.

[0066] One or more of the valves is (are) opened, as appropriate to theparticular procedure being performed on the tank car. A valve closureassembly 50 can be associated with the handle of any opened valve. Theefficient geometry of valve closure assembly 50 allows multiple valveclosure assemblies to be used concurrently. In this way a respectiveindividual valve closure assembly 50 can be associated with a respectivehandle so that if all four valves are opened, they can be automaticallyclosed by the respective valve closure assembly. The example shown inFIGS. 34-35 involves only a single valve closure assembly.

[0067] With hand screw 130 backed off sufficiently to provide aclearance from the distal end of shank 156 to side wall 132 of clampassembly 52 that is sufficiently greater than the thickness of the rimof protective housing side wall 162, handle 74 can be grasped toposition the valve closure assembly over protective housing 160 withbracket assembly 122 positioned over the housing side wall rim and thedownwardly open throat of the bracket assembly aligned with the rim andwith motor head 56 positioned over valve V1 and direct drive adapter 180aligned with handle A1. The valve closure assembly is then lowered untiltop wall 136 of bracket assembly 122 comes to rest on the top edgesurface of the housing side wall rim and adapter 180 comes intoengagement with handle A1. Turning knob 159 of hand screw 130 is thengrasped and turned to advance shank 156 against the outside of thehousing rim thereby locking clamp assembly 52 to the protective cover.Other apparatus of the valve closure system that is not shown in thedrawings is able to operate motor 58 when handle A1 is to be operated toclose valve V1. During mounting of assembly 50 on a tank car, the linearbearings facilitate the ability of positioning mechanism 54 to achievethe desired positioning of motor head 56 relative to clamp assembly 52.They also facilitate any movement that may occur when motor 58 isoperated, such as vertical motion arising from valve handle travel asthe valve handle is turning. The linear bearings are commerciallyavailable products that incorporate circulating balls. Assembly 50 alsoadapts to a range of variations in valve location, a range in departureof a valve axis from vertical, and a range of thickness of theprotective housing rim, without compromising the ability of the assemblyto close an open valve.

[0068] Direct drive adapter 180 has features for fitting to handle A1.As motor 58 operates to turn the handle via adapter 180, the handle mayor may not translate vertically as it is turning. The range of verticaltravel of pillow block 100 on rod 114 and a proper vertical setting ofmotor head 56 on tie rod 64 will enable the motor head to travelvertically with the valve handle so that the driving relation of theadapter to the handle is maintained until the valve is fully closed.

[0069] FIGS. 36-39 show direct drive adapter 180. It comprises acylindrical hub 182 with a square drive hole 184 for fitting onto motorshaft 91. A transverse hole 186 is arranged for registration with a holein the motor shaft so that hitch pin 93 can pass through both holes topin the adapter to the motor shaft. A base plate 188 at the end of hub182 carries two drive pins 190 on the face of the base plate that isopposite hub 182. Drive pins 190 are arranged in a geometric patternthat allows them to fit into diametrically opposite holes 192 in thehandles when assembly 50 is associated with one of them (see FIG. 34).

[0070] Because positioning mechanism 54 also endows the valve closureassembly with the ability to position motor head 56 at varioushorizontal distances from vertical rod 114, it becomes possible to mountclamp assembly 52 within a range of locations around the rim of theprotective housing with respect to a particular valve. This can be anaid to mounting of a valve closure assembly, particularly when multiplevalve closure assemblies are used on a single tank car.

[0071] Positioning mechanism 54 is therefore capable of selectivelypositioning adapter 180 relative to the clamp assembly 52 to establish aspatial relationship of each to the other for enabling the clampassembly to be placed at a desired location on dome wall 162 and theadapter to engage a valve handle. Positioning mechanism 54 comprisesthree degrees of freedom of motion for establishing the spatialrelationship of the adapter to the mounting of assembly 50 on wall 162that is provided by clamp assembly 52. Two of those degrees of freedomof motion are in a horizontal plane of reference. They are provided ascircular translation along a horizontal arc by the ability of pillowblock 100 to turn on rod 114 about the vertical rod axis and as lineartranslation of rods 92 horizontally on pillow block 100. The thirddegree of freedom of motion is provided as vertical translation by theability of pillow block 100 to travel vertically on rod 114.

[0072] Overall weight is reduced by using aluminum as the material of anumber of the individual parts, such as clamp parts 124, 126, 128 andmotor mount parts 62, 68. An optional trapezoidal hole 170 in theupwardly pointing tongue of bracket 68 lightens its weight. Certainindividuals will be able to carry a valve closure assembly 50 bygrasping handle 74, and able to install it on a tank car without help. Ahole 172 near the tip end of the tongue of bracket 68 is available forattachment of an end of a lift or winch cable that can be used as an aidin lifting the valve closure assembly. Rectangular holes in side walls132, 134 of bracket part 126 can lighten its weight. Assembly 50 can beused with a valve handle that is different from the ones shown by usingan adapter that like adapter 180 attaches directly to motor shaft 91using hitch pin 93, but differs in how it mates with the particularvalve handle.

[0073] Further examples of various adapters are disclosed in commonlyowned, non-provisional patent application of the same inventors,“Adapters And Adapter Systems For Valve Closure Systems And ValveClosure Assemblies”, Ser. No. ______, of even date, (Attorney DocketPowellUS09).

[0074] While a presently preferred embodiment of the invention has beenillustrated and described, it should be appreciated that principles ofthe invention are applicable to all embodiments that fall within thescope of the claims that follow hereinafter.

What is claimed is:
 1. An assembly for turning an external handle of atank dome valve about a vertical axis, the assembly comprising: amounting for removably mounting the assembly on a tank dome, an adapteroperated by a motor for engaging the valve handle and turning the handlewhen the motor operates, and a positioning mechanism for selectivelypositioning the adapter relative to the mounting to establish a spatialrelationship of each to the other for enabling the mounting to be placedat a desired location on the dome and the adapter to engage the valvehandle, wherein the positioning mechanism comprises two degrees offreedom of motion in a horizontal plane for establishing the spatialrelationship of the adapter to the mounting in the horizontal plane. 2.An assembly as set forth in claim 1 in which the mounting comprises aclamping mechanism for fitting and clamping onto a rim of an uprightwall of the dome bounding a zone of the dome containing the valve.
 3. Anassembly as set forth in claim 2 in which the positioning mechanismcomprises a first part supported on the clamping mechanism and a secondpart that comprises an association with the first part for providing thepositioning mechanism with a first of the two degrees of freedom ofmotion that extends along a circular arc centered on the first part. 4.An assembly as set forth in claim 3 in which the first part comprises anupright post on the clamping mechanism and the association of the secondpart with the first part comprises a joint that allows the second partto turn on the post about a vertical axis of the post for causing thefirst degree of freedom of motion to extend along a horizontal circulararc centered on the vertical axis.
 5. An assembly as set forth in claim4 in which the joint comprises a linear bearing between the post and thesecond part to allow the second part not only to turn on the post aboutthe vertical axis of the post but also to be positioned vertically alongthe post.
 6. An assembly as set forth in claim 5 in which thepositioning mechanism further comprises a third part that comprises anassociation with the second part for providing the positioning mechanismwith a second of the two degrees of freedom of motion.
 7. An assembly asset forth in claim 6 in which the association of the third part with thesecond part comprises a joint through which the third part is supportedon the second part and which provides for selective positioning of thethird part relative to the second part along a horizontal linear axis.8. An assembly as set forth in claim 7 in which the second partcomprises a central zone having a vertical through-hole in which thebearing is disposed and zones at either lateral side of the central zoneeach having a respective horizontal through-hole containing a respectivelinear bearing, and the third part comprises rods received in the linearbearings in the horizontal through-holes.
 9. An assembly as set forth inclaim 8 in which the motor is mounted on a horizontal platform of abracket that is attached to a bar that ties together ends of portions ofthe rods that extend from one longitudinal end of the second part, thebracket comprises a vertical wall extending upright from the platformand disposed between the motor and the second part, and the assemblyfurther includes a handle for lifting the assembly attached to thevertical wall in vertically spaced relation to the horizontal platformand extending transversely of the vertical wall in a direction away fromthe motor.
 10. An assembly as set forth in claim 9 in which the motorcomprises an air motor having an output shaft that turns about avertical axis and that protrudes through an aperture in the horizontalplatform to extend below the horizontal platform, and the adapterattaches to the output shaft below the horizontal platform.
 11. Anassembly as set forth in claim 9 including another bar that tiestogether ends of portions of the rods that extend from a longitudinalend of the second part opposite the one longitudinal end, and bumpersdisposed between each bar and the second part for preventing either barfrom hitting the second part.
 12. An assembly as set forth in claim 3 inwhich the positioning mechanism further comprises a third part thatcomprises an association with the second part for providing thepositioning mechanism with a second of the two degrees of freedom ofmotion, and the association of the third part with the second partcomprises a joint through which the third part is supported on thesecond part and which provides for selective positioning of the thirdpart relative to the second part along a horizontal linear axis.
 13. Anassembly as set forth in claim 1 in which the positioning mechanismcomprises a first part supported on the mounting, a second part thatcomprises an association with the first part for providing thepositioning mechanism with a first of the two degrees of freedom ofmotion, and a third part that comprises an association with the secondpart for providing the positioning mechanism with a second of the twodegrees of freedom of motion.
 14. An assembly as set forth in claim 13in which the association of second part with the first part comprises ajoint that allows the second part to be selectively positioned on thefirst part along a circular arc centered on the first part.
 15. Anassembly as set forth in claim 14 in which the joint that allows thesecond part to be selectively positioned on the first part along acircular arc centered on the first part comprises a joint that allowsthe second part to be selectively positioned on the first part along ahorizontal circular arc centered on the first part.
 16. An assembly asset forth in claim 15 in which the association of the third part withthe second part comprises a joint through which the third part issupported on the second part and which provides for selectivepositioning of the third part relative to the second part along a linearaxis.
 17. An assembly as set forth in claim 16 in which the first partcomprises an upright post on the mounting, and the joint that allows thesecond part to be selectively positioned on the first part along ahorizontal circular arc comprises a joint that allows the second partboth to turn on the post as it is selectively positioned along thecircular horizontal arc centered on the vertical axis and also to bepositioned vertically along the post.
 18. An assembly as set forth inclaim 13 in which the association of the third part with the second partcomprises a joint through which the third part is supported on thesecond part and which provides for selective positioning of the thirdpart relative to the second part along a linear axis.
 19. An assembly asset forth in claim 18 in which the joint through which the third part issupported on the second part and which provides for selectivepositioning of the third part relative to the second part along a linearaxis comprises a joint that provides for selective positioning of thethird part relative to the second part along a horizontal linear axis.20. An assembly as set forth in claim 1 in which one of the degrees offreedom of motion describes a circular arc in the horizontal plane andthe other of the degrees of freedom of motion describes a straight linein the horizontal plane.
 21. An assembly for turning an external handleof a tank dome valve about a vertical axis, the assembly comprising: amounting for removably mounting the assembly on a tank dome, an adapteroperated by a motor for engaging the valve handle and turning the handlewhen the motor operates, and a positioning mechanism for selectivelypositioning the adapter relative to the mounting to establish a spatialrelationship of each to the other for enabling the mounting to be placedat a desired location on the dome and the adapter to engage the valvehandle, wherein the positioning mechanism comprises three degrees offreedom of motion for establishing the spatial relationship of theadapter to the mounting.
 22. An assembly as set forth in claim 21 inwhich two of the three degrees of freedom of motion establish thatportion of the spatial relationship within a plane of reference, and thethird degree of freedom of motion establishes that portion of thespatial relationship transverse to the plane of reference.
 23. Anassembly as set forth in claim 22 in which the plane of reference is ahorizontal plane.
 24. An assembly as set forth in claim 21 in which twoof the three degrees of freedom of motion are along non-parallelstraight lines, and the third degree of freedom of motion is along acircular arc.
 25. An assembly as set forth in claim 24 in which one ofthe straight lines is vertical, and the other, horizontal.
 26. Anassembly as set forth in claim 24 in which the circular arc is centeredon a vertical axis.
 27. A method of associating a valve operatingassembly with a fluid-containing tank for enabling an adapter that isoperated by a motor of the valve operating assembly to turn an externalhandle of a valve on the tank about an axis of turning while a mountingof the assembly is supporting the assembly on the tank, the methodcomprising: relatively positioning the mounting and the adapter via apositioning mechanism of the valve operating assembly that has twodegrees of freedom of motion in a plane of reference that isperpendicular to the axis of turning to establish a spatial relationshipof the mounting and motor to each other in the plane of reference forplacing the adapter in engagement with the valve handle and placing themounting at a desired location on the tank.
 28. A method as set forth inclaim 27 in which the relatively positioning step comprises relativelypositioning the mounting and the adapter via the positioning mechanismin a plane of reference that is horizontal.
 29. A method of associatinga valve operating assembly with a fluid-containing tank for enabling anadapter operated by a motor of the valve operating assembly to turn avalve on the tank about an axis of turning while a mounting of theassembly is supporting the assembly on the tank, the method comprising:relatively positioning the mounting and the adapter via a positioningmechanism of the valve operating assembly that has three degrees offreedom of motion to establish a spatial relationship of the mountingand motor to each other for placing the adapter in engagement with thevalve handle and placing the mounting at a desired location on the tank.30. A method of associating a valve operating assembly comprising amounting, a positioning mechanism, and an adapter operated by a motorwith a dome of a fluid-containing tank comprising a valve having ahandle that is external to the tank and an upright wall spacedhorizontally from the valve handle for enabling the adapter to engagethe valve handle and turn the handle about an axis of turning while themounting is supporting the assembly at a desired location on the dome inhorizontally spaced relation to the valve handle, the method comprising:disposing the valve operating assembly vertically over the dome,lowering the assembly onto the dome, and causing the positioningmechanism to relatively position the mounting and the adapter to placethe adapter in engagement with the valve handle and to place themounting at a desired location on the upright wall.